JP2017112184A - Substrate for printed wiring board and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide: a substrate for a printed wiring board, which is relatively inexpensive, and relatively small in the decrease in adhesion between a base film and a metal layer with time; and a method for manufacturing the substrate for a printed wiring board.SOLUTION: A substrate for a printed wiring board according to an embodiment of the present invention comprises: a base film having an insulating property; and a metal layer laminated on at least one face of the base film. The base film includes cobalt atoms in a surface region ranging from an interface of the metal layer and the base film to a depth of 1 μm in a thickness direction, and the content of the cobalt atoms is 1-15 atomic%. A method for manufacturing a substrate for a printed wiring board according to another embodiment of the invention comprises the steps of: performing an alkali treatment on at least one face of a base film; bringing a cobalt ion-containing aqueous solution into contact with the at least one face of the base film after the alkali treatment step; and laminating a metal layer on the at least one face of the base film after the contact step.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a printed wiring board substrate and a method for manufacturing a printed wiring board substrate.

  For example, a metal layer made of metal or the like is laminated on at least one surface of an insulating base film made of resin or the like, and a conductive pattern is formed by etching the metal layer to form a printed wiring board. Printed wiring board substrates for obtaining are widely used.

  A printed wiring board having a high peel strength between the base film and the metal layer so that the metal layer does not peel from the base film when bending stress acts on the printed wiring board formed using such a printed wiring board substrate. Substrates are required.

  In recent years, with the miniaturization and high performance of electronic devices, it has been required to increase the density of printed wiring boards. In the printed wiring board having a high density, the conductive pattern easily peels off from the base film as the conductive pattern becomes finer. Therefore, there is a demand for a printed wiring board substrate that can form a fine conductive pattern and has excellent adhesion between a metal layer and a base film as a printed wiring board substrate that satisfies such a demand for higher density.

  In response to such a demand, a copper thin film layer is formed on at least one surface of the base film using, for example, a sputtering method, and a copper thick film layer is formed thereon using an electroplating method. Techniques for increasing the adhesion between the layer and the base film are known. However, when the metal layer is directly laminated on the base film, it is known that the metal atoms of the metal layer diffuse into the base film with time and the adhesion between the metal layer and the base film is lowered. .

  Therefore, a technique has been proposed in which a thin film of chromium is deposited by sputtering on the joint surface of the copper foil to the base film and thermocompression bonded to the base film (see Japanese Patent Application Laid-Open No. 2000-340911). In this way, by interposing a thin film of a metal different from the main metal of the metal layer at the interface between the metal layer and the base film, the movement of the main metal to the base film is hindered. The effect which suppresses the fall of the adhesiveness between the metal layer and base film by the diffusion to a base film of a metal atom is acquired.

JP 2000-340911 A

  In the configuration described in the above publication, a chromium thin film is formed on one surface of the copper foil by using a sputtering method, so that a vacuum facility is required, and costs for construction, maintenance, operation, etc. of the facility are high. . Further, in terms of equipment, there is a limit to increasing the size of the substrate.

  The present invention has been made based on the above-described circumstances, and is relatively inexpensive and relatively low in adhesion between the base film and the metal layer over time, and for printed wiring board substrates and printed wiring boards. It is an object to provide a method for manufacturing a substrate.

  A printed wiring board substrate according to an aspect of the present invention, which has been made to solve the above problems, is a printed wiring comprising an insulating base film and a metal layer laminated on at least one surface of the base film. It is a board | substrate for plates, Comprising: A cobalt atom is contained in the surface layer area | region of 1 micrometer in the thickness direction from the interface with the metal layer in the said base film, The content rate of this cobalt atom is 1 atomic% or more and 15 atomic% or less.

  Moreover, the manufacturing method of the printed wiring board board | substrate which concerns on another aspect of this invention made | formed in order to solve the said subject is the base film which has insulation, and the metal laminated | stacked on at least one surface of this base film A printed wiring board substrate comprising: a step of alkali-treating at least one surface of the base film; and a cobalt ion-containing aqueous solution on at least one surface of the base film after the alkali treatment step. A step of contacting, and a step of laminating a metal layer on at least one surface of the base film after the contacting step.

  The printed wiring board substrate according to one aspect of the present invention and the printed wiring board substrate obtained by the method for producing a printed wiring board substrate according to another aspect of the present invention are relatively inexpensive and have a base film and metal over time. The decrease in adhesion with the layer is relatively small.

FIG. 1 is a schematic cross-sectional view showing a printed wiring board substrate according to an embodiment of the present invention. FIG. 2 is a detailed schematic cross-sectional view of the printed wiring board substrate of FIG. FIG. 3 is a flowchart showing the procedure of the method for manufacturing the printed wiring board substrate of FIG.

[Description of Embodiment of the Present Invention]
A printed wiring board substrate according to an aspect of the present invention is a printed wiring board substrate comprising a base film having an insulating property and a metal layer laminated on at least one surface of the base film, wherein the base Cobalt atoms are contained in the surface layer region of 1 μm in the thickness direction from the interface with the metal layer in the film, and the content rate of the cobalt atoms is 1 atomic% or more and 15 atomic% or less.

  Since the substrate for a printed wiring board contains cobalt atoms within the above content rate range in the surface layer region from the interface with the metal layer in the base film to 1 μm in the thickness direction, this cobalt atom is a metal atom of the metal layer. Can be prevented from spreading into the base film. The treatment for containing the cobalt atom in the base film can be performed relatively easily, for example, by contacting the base film with a cobalt ion-containing aqueous solution. For this reason, the printed wiring board substrate is relatively inexpensive, but has a relatively small decrease in adhesion between the base film and the metal layer due to change over time.

  The metal layer may include a sintered body layer of metal particles. Thus, when the metal layer includes a sintered body layer of metal particles, the metal layer can be formed at a relatively low cost.

  The metal layer may include a plating layer. Thus, when the metal layer includes a plating layer, the metal layer can be made relatively dense and excellent in conductivity.

  The cobalt atom may be chemically bonded to the polymer constituting the base film. In this way, the cobalt atoms are chemically bonded to the polymer constituting the base film, thereby suppressing the metal atoms in the metal layer from reacting with the functional groups of the polymer constituting the base film and being incorporated into the polymer. Since it can do, it can prevent more reliably that the metal atom of a metal layer diffuses in a base film, and can suppress more reliably the fall of the adhesiveness of a base film and a metal layer.

  A printed wiring board substrate manufacturing method according to another aspect of the present invention is a printed wiring board substrate including an insulating base film and a metal layer laminated on at least one surface of the base film. A method of alkali-treating at least one surface of the base film, a step of bringing a cobalt ion-containing aqueous solution into contact with at least one surface of the base film after the alkali treatment step, and a base after the contact step Laminating a metal layer on at least one surface of the film.

  Since the method for manufacturing a printed wiring board substrate includes a step of bringing a cobalt ion-containing aqueous solution into contact with at least one surface of the base film after the alkali treatment step, the comparison is formed on the polymer constituting the base film by the alkali treatment. It is thought that cobalt is chemically bonded to a polymer constituting the base film by a reaction between a functional group rich in mechanical reactivity and cobalt ions in an aqueous solution. Thereby, a cobalt atom can be contained in the surface layer area | region of a base film, and it can suppress that the metal atom of a metal layer diffuses in a base film with this cobalt atom. For this reason, the printed wiring board substrate obtained by the method for manufacturing a printed wiring board substrate is relatively inexpensive, but has a relatively small decrease in adhesion between the base film and the metal layer due to aging.

  The cobalt ion-containing aqueous solution may be a cobalt acetate aqueous solution. Thus, since the cobalt ion-containing aqueous solution is a cobalt acetate aqueous solution, cobalt atoms can be contained in the surface layer region of the base film relatively efficiently, so that the adhesion between the base film and the metal layer due to aging changes. Can be more effectively suppressed.

  The metal layer laminating step may include a step of applying and heating the metal particle dispersion on at least one surface of the base film. As described above, the metal layer laminating step includes a step of applying and heating the metal particle dispersion liquid to at least one surface of the base film, so that a large-scale facility is not required and it is relatively simple and inexpensive. Further, a metal layer can be laminated on at least one surface of the base film.

  Here, the “atom content” refers to, for example, X-ray photoelectron spectroscopy (ESCA: Electron Spectroscopy for Chemical Analysis or XPS: X-ray Photoelectron Spectroscopy), energy dispersive X-ray spectroscopy (EDX: energypipe). ray Spectroscopy or EDS (Energy Dispersive X-ray Spectroscopy), electron probe microanalysis (EPMA), time-of-flight secondary ion mass spectrometry (TOF-SIMSSonFiSmFonSigMitSonFiSonFrM). two Ion mass spectrometry (SIMS: Secondary Ion Mass Spectrometry), Auger electron spectroscopy can be measured by (AES Auger Electron Spectroscopy) and the like. In the case of X-ray photoelectron spectroscopy, the measurement is performed by scanning the cross section with the X-ray source being an aluminum metal K alpha ray, the beam diameter being 50 μm, the X-ray incident angle with respect to the surface to be analyzed being 45 °. be able to. As the measuring device, for example, a scanning X-ray photoelectron spectrometer “Quantera” manufactured by ULVAC-Phi can be used.

[Details of the embodiment of the present invention]
Hereinafter, embodiments of a printed wiring board substrate and a printed wiring board manufacturing method according to the present invention will be described in detail with reference to the drawings.

[Substrates for printed wiring boards]
As shown in FIG. 1, a printed wiring board substrate according to an embodiment of the present invention includes an insulating base film 1 and a metal layer 2 laminated on one surface (surface) of the base film 1. Prepare.

<Base film>
The base film 1 of the printed wiring board substrate contains cobalt atoms in the surface layer region A of 1 μm in the thickness direction from the interface with the metal layer 2. The cobalt atoms contained in the surface layer region A of the base film 1 inhibit the metal atoms constituting the metal layer 2 from diffusing into the base film 1. Moreover, since the process which makes the surface layer area | region A of the base film 1 contain a cobalt atom is comparatively easy, the said board | substrate for printed wiring boards can be provided comparatively cheaply. Therefore, although the printed wiring board substrate is relatively inexpensive, the decrease in adhesion between the base film 1 and the metal layer 2 due to a change with time is relatively small.

  The lower limit of the content of cobalt atoms in the surface region A is 1 atomic%, preferably 2 atomic%, and more preferably 5%. On the other hand, the upper limit of the cobalt atom content in the surface layer region A is 15 atomic%, preferably 13 atomic%, and more preferably 12%. When the content of cobalt atoms in the surface layer region A is less than the lower limit, the diffusion of metal atoms of the metal layer 2 into the base film 1 cannot be sufficiently prevented, and the base film 1 and the metal layer 2 are adhered to each other due to a change over time. There is a possibility that deterioration of the property cannot be sufficiently suppressed. Conversely, when the content of cobalt atoms in the surface layer region A exceeds the above upper limit, the adhesion between the base film 1 and the metal layer 2 in the initial stage (immediately after the production of the printed wiring board substrate) may be insufficient. is there.

  The thickness of the base film 1 is set by a printed wiring board using the printed wiring board substrate and is not particularly limited. For example, the lower limit of the average thickness of the base film 1 is preferably 5 μm, and 12 μm. Is more preferable. On the other hand, the upper limit of the average thickness of the base film 1 is preferably 2 mm, and more preferably 1.6 mm. When the average thickness of the base film 1 is less than the above lower limit, the strength of the base film 1 and thus the printed wiring board substrate may be insufficient. Conversely, when the average thickness of the base film 1 exceeds the above upper limit, the printed wiring board substrate may be unnecessarily thick.

  Examples of the material of the base film 1 include flexible resins such as polyimide, liquid crystal polymer, fluororesin, polyethylene terephthalate, and polyethylene naphthalate, paper phenol, paper epoxy, glass composite, glass epoxy, polytetrafluoroethylene, and glass. It is possible to use a rigid material such as a base material, a rigid flexible material in which a hard material and a soft material are combined, and the like. Among these, a polymer mainly composed of polyimide is particularly preferable because it has a high bonding force with a metal oxide or the like and is excellent in insulation and mechanical strength.

  Thus, when the base film 1 is comprised with a polymer, it is preferable that the said cobalt atom is chemically bonded to the polymer which comprises the base film 1. FIG. Since the cobalt atom is chemically bonded to the polymer constituting the base film 1, it can be suppressed that the metal atom of the metal layer 2 reacts with the functional group of the polymer constituting the base film 1 and is taken into the polymer. Thereby, it can prevent more reliably that the metal atom of the metal layer 2 diffuses in the base film 1, and can suppress more reliably the fall of the adhesiveness of a base film and a metal layer.

(Polyimide)
As the polyimide as the main component of the base film 1, thermosetting polyimide (also referred to as condensation type polyimide) or thermoplastic polyimide can be used. Among these, thermosetting polyimide is preferable from the viewpoint of heat resistance, tensile strength, tensile elastic modulus, and the like.

  The polyimide may be a homopolymer consisting of one type of structural unit or a copolymer consisting of two or more types of structural units, or a blend of two or more types of homopolymers. However, what has a structural unit represented by following formula (1) is preferable.

  The structural unit represented by the above formula (1) synthesizes polyamic acid, which is a polyimide precursor, using, for example, pyromellitic dianhydride and 4,4′-diaminodiphenyl ether, and imidizes it by heating or the like. It is obtained by doing.

  As a minimum of content of the above-mentioned structural unit, 10 mass% is preferred, 15 mass% is more preferred, and 18 mass% is still more preferred. On the other hand, as an upper limit of content of the said structural unit, 50 mass% is preferable, 40 mass% is more preferable, and 35 mass% is further more preferable. When the content of the structural unit is less than the lower limit, the printed wiring board substrate, and thus the printed wiring board formed using the printed wiring board substrate, may be insufficient in strength. Conversely, if the content of the structural unit exceeds the upper limit, the flexibility of the printed wiring board substrate may be insufficient.

  The base film 1 having polyimide as a main component preferably has at least an interface with the metal layer 2 modified so that a part of the polyimide imide ring is opened. Such modification can be performed by a known treatment method such as alkali treatment or plasma treatment.

  As a minimum of the ring-opening rate of the imide ring of the interface with the metal layer 2 of the base film 1, 3% is preferable and 15% is more preferable. On the other hand, the upper limit of the ring-opening rate of the imide ring at the interface with the metal layer 2 of the base film 1 is preferably 70% and more preferably 60%. When the ring-opening rate of the imide ring at the interface between the base film 1 and the metal layer 2 is less than the lower limit, the adhesion between the base film 1 and the metal layer 2 in the initial stage may be insufficient. On the contrary, when the ring opening rate of the imide ring at the interface with the metal layer 2 of the base film 1 exceeds the above upper limit, the strength of the base film 1 is insufficient, and the metal layer 2 may be easily peeled due to the substrate destruction. There is.

  In addition, the ring-opening rate of the imide ring at the interface between the base film 1 and the metal layer 2 can be calculated from the peak intensity showing the imide ring in the absorption intensity spectrum obtained by, for example, infrared absorption spectroscopy. . More specifically, the ring-opening rate of the imide ring at the interface between the base film 1 and the metal layer 2 is measured by an infrared total reflection absorption measurement method using a single reflection ATR (Attenuated Total Reflection) measurement device using a diamond prism. Can be measured.

In the absorption intensity spectrum at an incident angle of 45 ° by the infrared total reflection absorption measurement method, the peak intensity at a wave number of 1494 cm ^{−1 is} the peak intensity indicating the number of benzene rings, and even when the polyimide imide ring is opened. It is a value that does not change. On the other hand, the peak intensity at a wave number of 1705 cm ⁻¹ in the absorption intensity spectrum is a peak intensity indicating the number of carbonyl groups in the imide bond, and is a value that decreases as the imide ring of the polyimide is opened. Therefore, it is possible to estimate the ring opening of the polyimide imide ring from the ratio of the peak intensity at a wavenumber of 1705 cm ^-1 to the peak intensity at a wavenumber of 1494cm ^-1 in the absorption intensity spectrum. Specifically, ring-opening of the polyimide of the imide ring is proportional to the ratio of the peak intensity at a wavenumber of 1705 cm ^-1 to the peak intensity at a wavenumber of 1494cm ^-1 in the absorption intensity spectrum, when opening ratio of 0% The peak intensity ratio is about 1.1.

  Further, infrared absorption analysis of the interface between the base film 1 and the metal layer 2 can be performed by removing the metal layer 2 by etching using an acidic solution.

  As an acidic solution used for etching for removing the metal layer 2, an acidic etching solution generally used for removing the metal layer can be used, and examples thereof include a copper chloride solution, hydrochloric acid, sulfuric acid, and aqua regia.

  As a minimum of the temperature of the above-mentioned etching solution at the time of etching, 10 ° C is preferred and 20 ° C is more preferred. On the other hand, the upper limit of the temperature of the etching solution is preferably 90 ° C, more preferably 70 ° C. When the temperature of the etching solution is less than the lower limit, the time required for etching becomes long and workability may be deteriorated. On the contrary, when the temperature of the etching solution exceeds the upper limit, the energy cost for temperature adjustment may increase unnecessarily.

  The lower limit of the etching time is preferably 1 minute, and more preferably 10 minutes. On the other hand, the upper limit of the etching time is preferably 60 minutes, and more preferably 30 minutes. When the said etching time is less than the said minimum, there exists a possibility that the density | concentration of etching liquid may become high and it may become difficult to handle. Conversely, if the etching time exceeds the upper limit, workability may be reduced.

<Metal layer>
In the printed wiring board substrate, the metal layer 2 may include a sintered body layer of metal particles. The sintered layer of metal particles does not require a large-scale apparatus such as a vacuum facility, and can be formed relatively easily and inexpensively. For this printed wiring board, a sintered layer of metal particles is provided. The manufacturing cost of the substrate can be suppressed.

  The metal layer 2 may include a plating layer formed by metal lamination by plating (electroless plating or electroplating). By providing the plating layer, it is easy to make the metal layer 2 relatively inexpensive, dense and excellent in conductivity.

  Specifically, for example, as shown in FIG. 2, the metal layer 2 includes a sintered body layer 3 laminated on the surface of the base film 1 by sintering a plurality of metal particles, and the sintered body layer. The electroless plating layer 4 laminated on the surface of the electroless plating 3 and the electroplating layer 5 further laminated on the surface of the electroless plating layer 4 by electroplating can be used.

  As the main metal of the metal layer 2, for example, copper, nickel, aluminum, gold, silver or the like can be used. Among these, copper is preferably used as a relatively inexpensive metal that has good conductivity and excellent adhesion to the base film 1 and that can be easily patterned by etching. Moreover, when the main metal of the metal layer 2 is copper, the adhesiveness fall inhibitory effect with the metal layer 2 by making the surface layer area | region A of the base film 1 contain a cobalt atom becomes remarkable.

(Sintered body layer)
The sintered body layer 3 is formed by coating a modified surface of the base film 1 with a metal particle dispersion (ink) containing a plurality of metal particles whose main component is a metal that is a main metal of the metal layer 2 and It can be laminated on the surface of the base film 1 by firing. Thus, the metal layer 2 can be easily and inexpensively formed on the surface of the base film 1 by using the metal particle dispersion.

  As a minimum of the average particle diameter of the metal particle which forms the sintered compact layer 3, 1 nm is preferable and 30 nm is more preferable. On the other hand, the upper limit of the average particle diameter of the metal particles is preferably 500 nm, and more preferably 100 nm. When the average particle diameter of the metal particles is less than the lower limit, for example, the dispersibility and stability of the metal particles in the metal particle dispersion may be reduced, so that the metal particles can be uniformly laminated on the surface of the base film 1. May not be easy. On the contrary, when the average particle diameter of the metal particles exceeds the upper limit, the gap between the metal particles becomes large, and it may not be easy to reduce the porosity of the sintered body layer 3. The “average particle size” means a particle size at which the volume integrated value is 50% in the particle size distribution measured by the laser diffraction method.

  As a minimum of average thickness of sintered compact layer 3, 50 nm is preferred and 100 nm is more preferred. On the other hand, the upper limit of the average thickness of the sintered body layer 3 is preferably 2 μm, and more preferably 1.5 μm. When the average thickness of the sintered body layer 3 is less than the lower limit, there are many portions where metal particles do not exist in a plan view, and the conductivity may be lowered. Conversely, if the average thickness of the sintered body layer 3 exceeds the above upper limit, it may be difficult to sufficiently reduce the porosity of the sintered body layer 3, or the metal layer 2 may be unnecessarily thick. is there.

(Electroless plating layer)
The electroless plating layer 4 is formed by laminating the same metal as the main metal of the metal particles forming the sintered body layer 3 by performing electroless plating on the outer surface of the sintered body layer 3. The electroless plating layer 4 is formed so as to be impregnated into the sintered body layer 3. That is, voids inside the sintered body layer 3 are reduced by filling the gaps between the metal particles forming the sintered body layer 3 with the main metal by electroless plating. Thus, by filling the gap between the metal particles with the electroless plating metal, the gap between the metal particles is reduced, and the sintered body layer 3 is peeled off from the base film 1 with the gap as a starting point of fracture. Can be suppressed.

  The electroless plating layer 4 may be formed only inside the sintered body layer 3 depending on the electroless plating conditions. As a general theory, the lower limit of the average thickness of the electroless plating layer 4 formed on the outer surface of the sintered body layer 3 (not including the thickness of the plating metal inside the sintered body layer 3) is 0. 2 μm is preferable, and 0.3 μm is more preferable. On the other hand, the upper limit of the average thickness of the electroless plating layer 4 formed on the outer surface of the sintered body layer 3 is preferably 1 μm, and more preferably 0.7 μm. When the average thickness of the electroless plating layer 4 formed on the outer surface of the sintered body layer 3 is less than the lower limit, the electroless plating layer 4 is not sufficiently filled in the gaps between the metal particles of the sintered body layer 3. Since the porosity cannot be reduced sufficiently, the peel strength between the base film 1 and the metal layer 2 may be insufficient. On the contrary, when the average thickness of the electroless plating layer 4 formed on the outer surface of the sintered body layer 3 exceeds the above upper limit, the time required for the electroless plating becomes longer and the production cost may be unnecessarily increased. .

(Electroplating layer)
The electroplating layer 5 is formed by further laminating the main metal by electroplating on the outer surface side of the sintered body layer 3, that is, the outer surface of the electroless plating layer 4. By this electroplating layer 5, the thickness of the metal layer 2 can be adjusted easily and accurately. In addition, the thickness of the metal layer 2 can be increased in a short time by using electroplating.

  The thickness of the electroplating layer 5 is set according to the type and thickness of the conductive pattern required for the printed wiring board formed using the printed wiring board substrate, and is not particularly limited. In general, the lower limit of the average thickness of the electroplating layer 5 is preferably 1 μm and more preferably 2 μm. On the other hand, as an upper limit of the average thickness of the electroplating layer 5, 100 micrometers is preferable and 50 micrometers is more preferable. When the average thickness of the electroplating layer 5 is less than the lower limit, the metal layer 2 may be easily damaged. On the contrary, when the average thickness of the electroplating layer 5 exceeds the above upper limit, the printed wiring board substrate may be unnecessarily thick, or the printed wiring board substrate may be insufficiently flexible. is there.

[Method of manufacturing printed circuit board substrate]
As a specific example, the printed wiring board substrate is formed on the surface of the base film 1 after the alkali treatment step (step S1: alkali treatment step), as shown in FIG. It can be manufactured by a method comprising a step of contacting a cobalt ion-containing aqueous solution (step S2: contact step) and a step of laminating the metal layer 2 on the surface of the base film 1 after the contact step (step S3: lamination step). it can.

<Alkali treatment process>
In the alkali treatment step of step S1, by bringing the alkali liquid into contact with at least the surface of the base film 1 on which the metal layer 2 is to be laminated, the bond of the polymer constituting the base film 1 is weakened to impart reactivity. The base film 1 is made easy to contain a cobalt atom in the contact process mentioned later. Typically, a part of the imide ring of the base film 1 containing polyimide as a main component is opened. In the alkali treatment step, the entire base film 1 may be immersed in an alkali solution.

  Examples of the alkali solution used in this alkali treatment step include a sodium hydroxide aqueous solution and a potassium hydroxide aqueous solution, and a sodium hydroxide aqueous solution is generally used.

  The pH of the alkali solution used in the alkali treatment step can be, for example, 12 or more and 15 or less. Moreover, as contact time with the alkaline liquid of the base film 1, it can be 15 seconds or more and 10 minutes or less, for example. The temperature of the alkaline liquid can be set at, for example, 10 ° C. or more and 70 ° C. or less.

  Moreover, it is preferable that an alkali treatment process has a water washing process of washing the base film 1 with water. In this water washing step, the base film 1 is washed with water to remove the alkaline liquid adhering to the surface of the base film 1. Moreover, it is more preferable that the alkali treatment step has a drying step of drying the washing water after the water washing step. By evaporating the water in the base film 1, ions in the base film 1 are precipitated as metals and metal oxides, or combined with resin components of the base film 1 to stabilize the quality of the base film 1. can do.

<Contact process>
In the contact step of step S <b> 2, cobalt atoms are introduced into the surface layer region A of the base film 1 by bringing the cobalt ion-containing aqueous solution into contact with the alkali-treated surface of the base film 1. Specifically, a relatively reactive functional group formed by alkali treatment reacts with a polymer constituting the base film 1 and cobalt ions, and a cobalt atom chemically bonds to the polymer constituting the base film 1. Thus, it is considered that cobalt atoms are taken into the surface layer region A of the base film 1. In this contact step, the entire base film 1 may be immersed in an aqueous solution containing cobalt ions.

  Examples of the cobalt ion-containing aqueous solution include a cobalt acetate aqueous solution, a cobalt bromide aqueous solution, a cobalt chloride aqueous solution, a cobalt benzoate aqueous solution, and a cobalt nitrate aqueous solution. A cobalt acetate aqueous solution that is relatively easy to obtain and handle is preferably used. It is done. These aqueous solutions can be prepared by dissolving a cobalt compound or a hydrate thereof in water.

  The lower limit of the cobalt ion concentration of the aqueous solution containing cobalt ions is preferably 0.05 mol / L, more preferably 0.1 mol / L. On the other hand, the upper limit of the cobalt ion concentration of the aqueous solution containing cobalt ions is preferably 2 mol / L, and more preferably 1 mol / L. When the cobalt ion concentration of the cobalt ion-containing aqueous solution is less than the lower limit, the processing time may be long, and the productivity of the printed wiring board substrate may be insufficient. On the contrary, when the cobalt ion concentration of the cobalt ion-containing aqueous solution exceeds the above upper limit, the adjustment of the cobalt atom content rate may not be easy.

  As a minimum of the temperature of cobalt ion content aqueous solution, 5 ° C is preferred and 10 ° C is more preferred. On the other hand, as an upper limit of the temperature of cobalt ion containing aqueous solution, 60 degreeC is preferable and 45 degreeC is more preferable. When the temperature of cobalt ion containing aqueous solution is less than the said minimum, there exists a possibility that productivity of the said board | substrate for printed wiring boards may become inadequate because processing time becomes long. Conversely, when the temperature of the cobalt ion-containing aqueous solution exceeds the above upper limit, the adjustment of the cobalt atom content rate may not be easy, and the energy cost for temperature adjustment may increase unnecessarily.

  As a minimum of contact time of cobalt ion content aqueous solution to base film 1, 0.5 minutes are preferred and 1 minute is more preferred. On the other hand, the upper limit of the contact time of the cobalt ion-containing aqueous solution to the base film 1 is preferably 10 minutes, and more preferably 5 minutes. When the contact time of the cobalt ion-containing aqueous solution to the base film 1 is less than the lower limit, it is necessary to increase the concentration of the cobalt ion-containing aqueous solution, so that the handling may not be easy. On the contrary, when the contact time of the cobalt ion containing aqueous solution to the base film 1 exceeds the said upper limit, there exists a possibility that the productivity of the said board | substrate for printed wiring boards may become inadequate.

  The cobalt ion concentration of the cobalt ion-containing aqueous solution, the temperature, and the optimal contact time to the base film 1 influence each other and vary depending on the conditions of the alkali treatment, but the above-described surface layer region A of the base film 1 What is necessary is just to select suitably so that a cobalt atom content rate can be achieved.

<Lamination process>
The stacking step of step S3 includes the step of forming the sintered body layer 3 by applying and heating a metal particle dispersion containing a plurality of metal particles, so that the metal layer can be formed relatively inexpensively. preferable. Moreover, it is preferable that a lamination process has the process of forming the electroless-plating layer 4 by electroless plating, and the process of forming the electroplating layer 5 by electroplating.

(Sintered body layer forming step)
As the metal particle dispersion used in the sintered body layer forming step, a liquid containing a dispersion medium of metal particles and a dispersant for uniformly dispersing the metal particles in the dispersion medium is preferably used. By using the metal particle dispersion liquid in which the metal particles are uniformly dispersed in this way, the metal particles can be uniformly attached to the surface of the base film 1, and the uniform sintered body layer 3 is formed on the surface of the base film 1. Can be formed.

  The metal particles contained in the metal particle dispersion can be produced by a high temperature treatment method, a liquid phase reduction method, a gas phase method, etc., but a liquid phase reduction method capable of producing particles having a uniform particle size at a relatively low cost. It is preferable to use what is manufactured by.

  The dispersant contained in the metal particle dispersion is not particularly limited, but a polymer dispersant having a molecular weight of 2,000 to 300,000 is preferably used. Thus, by using the polymer dispersant having a molecular weight in the above range, the metal particles can be dispersed well in the dispersion medium, and the film quality of the obtained sintered body layer 3 is dense and has no defects. Can be. When the molecular weight of the dispersant is less than the lower limit, there is a possibility that the effect of preventing the aggregation of the metal particles and maintaining the dispersion may not be obtained. As a result, the sintered body layer laminated on the base film 1 There is a possibility that 3 cannot be made dense and has few defects. On the contrary, when the molecular weight of the dispersant exceeds the upper limit, the bulk of the dispersant is too large, and during heating performed after application of the metal particle dispersion, there is a risk of inhibiting the sintering of the metal particles and generating voids. is there. Moreover, when the volume of a dispersing agent is too large, there exists a possibility that the denseness of the film quality of the sintered compact layer 3 may fall, or the decomposition residue of a dispersing agent may reduce electroconductivity.

  The dispersant preferably does not contain sulfur, phosphorus, boron, halogen, and alkali from the viewpoint of preventing deterioration of parts. Preferred dispersants are those having a molecular weight in the above range, amine-based polymer dispersants such as polyethyleneimine and polyvinylpyrrolidone, and hydrocarbon-based hydrocarbons having a carboxylic acid group in the molecule such as polyacrylic acid and carboxymethylcellulose. Polar groups such as polymer dispersants, poval (polyvinyl alcohol), styrene-maleic acid copolymers, olefin-maleic acid copolymers, or copolymers having a polyethyleneimine moiety and a polyethylene oxide moiety in one molecule The polymer dispersing agent which has can be mentioned.

  The dispersant can also be added to the reaction system in the form of a solution dissolved in water or a water-soluble organic solvent. As a content rate of a dispersing agent, 1 to 60 mass parts is preferable per 100 mass parts of metal particles. The dispersing agent surrounds the metal particles to prevent aggregation and disperse the metal particles satisfactorily. However, when the content of the dispersing agent is less than the lower limit, the aggregation preventing effect may be insufficient. On the contrary, when the content ratio of the dispersant exceeds the upper limit, in the heating step after the application of the metal particle dispersion, excess dispersant may inhibit the sintering of the metal particles, and voids may be generated. In addition, the decomposition residue of the polymer dispersant may remain as an impurity in the sintered body layer 3 to reduce the conductivity.

  The content ratio of water serving as a dispersion medium in the metal particle dispersion is preferably 20 parts by mass or more and 1900 parts by mass or less per 100 parts by mass of the metal particles. The water of the dispersion medium sufficiently swells the dispersing agent to disperse the metal particles surrounded by the dispersing agent well, but when the content ratio of the water is less than the lower limit, the swelling effect of the dispersing agent by water May become insufficient. On the contrary, when the water content exceeds the upper limit, the metal particle ratio in the metal particle dispersion is reduced, and a good sintered body layer 3 having the necessary thickness and density on the surface of the base film 1 is obtained. There is a possibility that it cannot be formed.

  Various organic solvents that are water-soluble can be used as the organic solvent blended into the metal particle dispersion as necessary. Specific examples thereof include alcohols such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, sec-butyl alcohol and tert-butyl alcohol, ketones such as acetone and methyl ethyl ketone, Examples thereof include polyhydric alcohols such as ethylene glycol and glycerin and other esters, and glycol ethers such as ethylene glycol monoethyl ether and diethylene glycol monobutyl ether.

  The content ratio of the water-soluble organic solvent in the metal particle dispersion is preferably 30 parts by mass or more and 900 parts by mass or less per 100 parts by mass of the metal particles. When the content ratio of the water-soluble organic solvent is less than the lower limit, the effects of adjusting the viscosity and vapor pressure of the dispersion with the organic solvent may not be sufficiently obtained. Conversely, when the content ratio of the water-soluble organic solvent exceeds the above upper limit, the swelling effect of the dispersant by water becomes insufficient, and the metal particles may aggregate in the metal particle dispersion.

  As a method for applying the metal particle dispersion liquid to the base film 1, conventionally known application methods such as a spin coating method, a spray coating method, a bar coating method, a die coating method, a slit coating method, a roll coating method, and a dip coating method are used. Can be used. Further, for example, the metal particle dispersion may be applied to only a part of the surface of the base film 1 by screen printing, a dispenser, or the like.

  And the coating film of the metal particle dispersion liquid which apply | coated the metal particle dispersion liquid to the base film 1 is heated. As a result, the solvent dispersant in the metal particle dispersion is evaporated or thermally decomposed, and the remaining metal particles are sintered and the sintered body layer 3 fixed to the surface of the base film 1 is obtained. In addition, it is preferable to dry the coating film of a metal particle dispersion before the said heating.

  The sintering is preferably performed in an atmosphere containing a certain amount of oxygen. The lower limit of the oxygen concentration in the atmosphere during sintering is preferably 1 volume ppm, and more preferably 10 volume ppm. On the other hand, the upper limit of the oxygen concentration is preferably 10,000 volume ppm, more preferably 1,000 volume ppm. When the oxygen concentration is less than the lower limit, the amount of metal oxide generated in the vicinity of the interface of the sintered body layer 3 is reduced, and the adhesion between the base film 1 and the sintered body layer 3 may not be sufficiently improved. is there. Conversely, when the oxygen concentration exceeds the upper limit, the metal particles are excessively oxidized and the conductivity of the sintered body layer 3 may be reduced.

  As a minimum of the above-mentioned sintering temperature, 150 ° C is preferred and 200 ° C is more preferred. On the other hand, the upper limit of the sintering temperature is preferably 500 ° C, more preferably 400 ° C. When the said sintering temperature is less than the said minimum, between metal particles cannot be connected, and when the next electroless-plating layer 4 is formed, there exists a possibility that the sintered compact layer 3 may collapse | crumble. Conversely, when the sintering temperature exceeds the upper limit, the base film 1 may be deformed.

(Electroless plating layer formation process)
In the electroless plating layer forming step, the electroless plating layer 4 is formed by performing electroless plating on the surface of the sintered body layer 3 laminated on the surface of the base film 1 in the sintered body layer forming step.

  In addition, it is preferable to perform the said electroless-plating with processes, such as a cleaner process, a water washing process, an acid treatment process, a water washing process, a pre-dip process, an activator process, a water washing process, a reduction process, a water washing process, for example.

  Moreover, after forming the electroless-plating layer 4 by electroless plating, it is preferable to heat-process further. When heat treatment is performed after the formation of the electroless plating layer 4, the metal oxide or the like in the vicinity of the interface of the sintered body layer 3 with the base film 1 further increases, and the adhesion between the base film 1 and the sintered body layer 3. Becomes even larger. The heat treatment temperature and oxygen concentration after electroless plating can be the same as the heating temperature and oxygen concentration in the sintered body layer forming step.

(Electroplating layer forming process)
In the electroplating layer forming step, the electroplating layer 5 is laminated on the outer surface of the electroless plating layer 4 by electroplating. In this electroplating layer forming step, the thickness of the entire metal layer 3 is increased to a desired thickness.

  In this electroplating, for example, a conventionally known electroplating bath corresponding to a metal to be plated such as copper, nickel, silver or the like is used, and appropriate conditions are selected. Can be made to form.

<Advantages>
As described above, the printed wiring board substrate contains cobalt atoms in the content range in the surface layer region A of 1 μm in the thickness direction from the interface with the metal layer 2 in the base film 1. The atoms suppress the diffusion of metal atoms in the metal layer 2 into the base film 1. Since the above-described contact step for containing cobalt atoms in the base film 2 can be performed relatively easily, the printed wiring board substrate is relatively inexpensive, and the base film 1 and the metal layer due to changes over time. 2 is relatively small.

[Other Embodiments]
The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is not limited to the configuration of the embodiment described above, but is defined by the scope of the claims, and is intended to include all modifications within the meaning and scope equivalent to the scope of the claims. The

  The printed wiring board substrate may be manufactured by a method different from the method for manufacturing the printed wiring board shown in FIG. For example, the printed wiring board substrate may be manufactured by omitting the alkali treatment step, and the surface of the base film is modified by, for example, plasma treatment instead of the alkali treatment. May be.

  Furthermore, the detailed structure of the metal layer in the said printed wiring board board | substrate and the lamination | stacking method are arbitrary. Specifically, the metal layer of the printed wiring board substrate may not include one or more of the sintered body layer, the electroless plating layer, and the electroplating layer, and the metal film is heated on the base film. It may be a crimped one.

  The printed wiring board substrate may be a double-sided board in which metal layers are laminated on both sides of the base fill, or a multilayer board including a plurality of base films or insulating layers and three or more metal layers. When a plurality of metal layers are provided, the printed wiring board substrate only needs to have a configuration in which any of the surface layer regions of the base film has a cobalt atom content within the above range.

  EXAMPLES Hereinafter, although this invention is explained in full detail based on an Example, this invention is not interpreted limitedly based on description of this Example.

  In the following manner, the surface of the polyimide base film is alkali-treated and then cobalt atoms are added to the surface layer region, and then a printed wiring board substrate prototype No. 1-No. 14 was produced. Prototype No. of these printed wiring board substrates 1-No. In the preparation process of No. 14, the ring opening rate of the imide ring on the surface of the base film after the alkali treatment and the content rate of cobalt atoms in the surface layer region of 1 μm in the thickness direction from the surface of the base film after containing the cobalt atoms And measured. In addition, prototype No. of printed wiring board substrate is shown. 1-No. The peel strength between the base film and the metal layer immediately after the production of 14 was measured, and the peel strength between the base film and the metal layer after being subjected to a heat resistance test held at a temperature of 150 ° C. for 7 days was measured.

(Prototype No. 1)
A polyimide film “Kapton EN-S” (average thickness 25 μm) manufactured by Toray DuPont Co., Ltd. was used as a base film. Was washed three times with water and dried. Next, the alkali treatment was performed on a cobalt ion-containing aqueous solution (0.15 mol / L in terms of the molar concentration of cobalt ions) at a temperature of 25 ° C. in which cobalt acetate tetrahydrate was dissolved in water at a rate of 37.0 g / L. The base film was immersed for 90 seconds to contain cobalt atoms in the surface layer region, washed with water for 10 seconds three times, and then dried. Further, a printed wiring board is formed by laminating a sintered body layer of copper particles, an electroless plating layer and an electroplating layer in this order on the surface of the base film containing cobalt atoms. Prototype board No. 1 was obtained.

  The sintered body layer is coated with a copper particle dispersion having a copper concentration of 26% by mass, in which copper particles having an average particle diameter of 70 nm are dispersed in water, on the surface of the base film, and nitrogen having an oxygen concentration of 100 volume ppm The film was formed by heating at 350 ° C. for 30 minutes in the atmosphere, and the average thickness was 0.15 μm. An electroless plating layer was formed by performing electroless copper plating on the sintered body layer, and the total average thickness of the sintered body layer and the electroless plating layer was 0.45 μm. Further, an electroplating layer having an average thickness of 18 μm was laminated on the electroless plating layer to form a three-layer metal layer.

(Prototype Nos. 2-7)
Change alkali treatment time with aqueous sodium hydroxide solution, cobalt acetate tetrahydrate dissolution amount (cobalt ion concentration after dissolution) and immersion time in aqueous solution containing cobalt ions, and average particle size of copper particles forming sintered body layer Others are prototype No. Prototype No. of printed wiring board substrate under the same conditions as in No. 1. 2-7 were obtained. Note that the average thickness of the metal layer after electroless plating (the total average thickness of the sintered body layer and the electroless plating layer) was also different due to the difference in the average particle diameter of the copper particles. The differences between these conditions are summarized in Table 1.

(Prototype No. 8-14)
Furthermore, Kaneka's polyimide film “Apical NPI” (average thickness 25 μm) is used as the base film, alkali treatment time with aqueous sodium hydroxide solution, cobalt acetate tetrahydrate dissolved amount and immersion time in aqueous solution containing cobalt ions In addition, the average particle diameter of the copper particles forming the sintered body layer (and the average thickness of the metal layer after electroless plating) is changed, and the prototype of the printed wiring board substrate is the same under the same conditions. No. 8-14 were obtained. These conditions are also summarized in Table 1.

(Imide ring opening rate)
The ring opening rate of the polyimide imide ring is measured by using Thermo Fisher's infrared total reflection absorption measurement (FT-IR) device "Nicolet 8700" and SensIR's single reflection ATR accessory "Dura Scope" (diamond prism). Then, the absorption intensity spectrum in the range of the measurement wave number of 4000 to 650 cm ⁻¹ at an incident angle of 45 ° is measured by setting the resolution to 4 cm ⁻¹ with 16 times of integration (number of scans), and the obtained absorption From the intensity spectrum, the ratio of the peak intensity at the wave number of 1705 cm ^{−1 to} the peak intensity at the wave number of 1494 cm ⁻¹ was calculated, and the ratio of the peak intensity of the base film not subjected to the surface treatment was converted to 100%. This imide ring-opening rate is shown in Table 1.

(Cobalt content)
The content ratio of cobalt atoms in the surface layer region of the base film was determined by using a scanning X-ray photoelectron spectrometer “Quantera” manufactured by ULVAC-Phi, analyzing the X-ray source with an aluminum metal K alpha ray and a beam diameter of 50 μm. The X-ray incident angle with respect to the surface was measured as 45 °. The cobalt atom content is shown in Table 1.

(Peel strength)
The peel strength was measured by a method according to JIS-K-6854-2 (1999) “Adhesive—Peeling peel strength test method—2 parts: 180 degree peeling” with a resin film as a flexible adherend. The peel strength is shown in Table 1.

  As described above, prototype No. 1 containing cobalt atoms of 1 atomic% or more and 15 atomic% or less in the surface layer region of the base film. 1-3 and No.1. 8 to 10 both have a relatively large peel strength before and after the heat resistance test, and the change in the peel strength before and after the heat resistance test is small, resulting in a decrease in adhesion between the base film and the metal layer over time. Was confirmed to be relatively small. On the other hand, in the prototype No. in which the cobalt atom content in the surface layer region of the base film is greater than 15 atomic%. 4 and no. No. 11 had a small decrease in peel strength before and after the heat resistance test, but the peel strength before the heat resistance test was insufficient. Prototype No. which does not contain cobalt element in the surface layer region of the base film. 5-7 and no. In Nos. 12 to 14, although the peel strength before the heat resistance test was sufficient, the decrease in the peel strength by the heat resistance test was relatively large, and the decrease in the adhesion between the base film and the metal layer over time was relatively large. .

  The printed wiring board substrate and the printed wiring board manufacturing method according to the embodiment of the present invention can be widely used for manufacturing a printed wiring board.

DESCRIPTION OF SYMBOLS 1 Base film 2 Metal layer 3 Sintered body layer 4 Electroless plating layer 5 Electroplating layer A Surface layer area | region S1 Alkali process S2 Contact process S3 Lamination process

Claims (7)

An insulating base film;
A printed wiring board substrate comprising a metal layer laminated on at least one surface of the base film,
Cobalt atoms are contained in the surface layer region of 1 μm in the thickness direction from the interface with the metal layer in the base film,
A printed wiring board substrate having a cobalt atom content of 1 atomic% or more and 15 atomic% or less.   The printed wiring board substrate according to claim 1, wherein the metal layer includes a sintered body layer of metal particles.   The printed wiring board substrate according to claim 1, wherein the metal layer includes a plating layer.   The printed wiring board substrate according to claim 1, wherein the cobalt atom is chemically bonded to a polymer constituting the base film. An insulating base film;
A printed wiring board substrate comprising a metal layer laminated on at least one surface of the base film,
A step of alkali-treating at least one surface of the base film;
A step of bringing a cobalt ion-containing aqueous solution into contact with at least one surface of the base film after the alkali treatment step;
And a step of laminating a metal layer on at least one surface of the base film after the contact step.   The method for producing a printed wiring board substrate according to claim 5, wherein the cobalt ion-containing aqueous solution is a cobalt acetate aqueous solution.   The method for producing a printed wiring board substrate according to claim 5 or 6, wherein the metal layer laminating step includes a step of applying and heating the metal particle dispersion on at least one surface of the base film.

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